CN1223232C - Efficient determination of time of arrival of radio communication bursts - Google Patents

Abstract

The propagation time of a radio signal (93) from a radio transmitting station to a radio receiving station (91) is calculated based on the calculated correlation value (102), the calculated energy value (101) and a known energy value. A receiving station (91) receives a series of received signals (93) respectively corresponding to radio signaling bursts transmitted by the radio transmitting station. Each radio signaling burst includes a known signaling sequence. The calculated correlation value (102) indicates the correlation between the received signal and the known sequence, the calculated energy value (101) is calculated for the corresponding received signal, and the known energy value is the energy of the known sequence.

Description

Effectively determine the time that radio communication bursts arrives

Invention field

The present invention relates generally to determine the position of a mobile radio unit, and be particularly related to the radio signal measurement of the time of advent.

Background of invention

The ability of determining a mobile radio cell position provides many known advantages.The such location determination capabilities of exemplary use comprises security applications, and emergency response is used and the travelling direct application.Provide the routine techniques of location determination capabilities comprise the time of advent (TOA) and the time of advent poor (TDOA) technology.

With reference to Fig. 1,, then can in using, conventional TOA and TDOA use this time of advent if radio reception station can be determined to stand in the time that a wireless signal of scheduled time emission receives in this receiving station by a radio transmission.Because the time of emission is known, thus can determine time of arriving, for example, by means of determine with two stations between the relevant propagation time of radio channel.This propagation time takes advantage of the light velocity to produce the calculating of geometric distance between two stations afterwards.If a plurality of fixed position receiving station measured by the signal of mobile cell site emission time of advent separately, if perhaps the measurement of a mobile receiving station is by the time of advent of a plurality of signals of a plurality of fixed position each spontaneous emission of cell site, then the distance of each from this mobile radio station to a plurality of fixed stations can be determined, and is used for calculating the position of this mobile radio station in a usual manner.

As an example, the global system (GSM) that just is used for mobile communication is now described the up link approximate measure time of advent, and GSM is the example of wireless communication system, wherein can use the up link measuring technique time of advent.When the position of a mobile unit (also referring to mobile radio station) is determined in an applications (or GSM network itself) decision, a mobile positioning center forces (by a base station controller) this mobile unit to carry out conventional asynchronous delivering, this mobile unit emission is up to 70 uplink access bursts thus, burst of every tdma frame (that is burst of per 8 time slots).Mobile unit is launched this access burst and is attempted to deliver order in accordance with this different portion.

Mobile positioning center (MLC) is ordered a plurality of Location Measurement Units (LMU) to catch this access burst and is measured each burst time of advent at each MLU.LMU measures its time of advent and these measuring reliability estimations is offered MLC afterwards.For calculating the position of this mobile radio station, MLC uses and arrives time value and corresponding reliability parameter, the geographical position coordinate of LMU, with relevant when the respective inner of LMU the information of the time difference in the base.For example, each MLU can be equipped with an absolute time benchmark (for example, a global positioning system (GPS) clock), and in the case, LMU makes that together by synchronously the relative time difference in LMU is not a factor when MLC calculates mobile station location.

Under the normal condition, burst comprises two parts, and a part is a known array, is commonly referred to as a training sequence, and another part comprises that to receiver be unknown data.When the TOA of one group of burst of estimation, noise disturbs and multipath transmisstion is a subject matter, and under the signal situation high to noise and interference ratio (SNIR), multipath transmisstion must be a main difficulty, and existing various technology provide TOA to estimate problem.Opposite situation is when the very low situation of SNIR.In this case, ignore the influence of multipath transmisstion usually, and all make great efforts to concentrate on " searching " burst, promptly with 0.5-1 mark space order of magnitude precision estimation TOA.Sometimes this is called that training sequence detects or burst is synchronous.

Be desirable to provide and under high and low two kinds of situations of SNIR, work the estimation of TOA.The present invention proposes TOA estimation problem under low SNIR condition especially, promptly detects problem.

I the burst that consideration is launched on a channel, each burst comprise the identical finite sequence S (t) (for example, a training sequence) of known bits, and with receiver the unknown other the position together.Burst is delayed a propagation time between transmitter and receiver, as mentioned above, this is the target of determining.By X _i(t) indication is to the received signal of given burst i, and t is (continuous) time here.For simplicity, all functions described here will be continuous in time.Because frequency band is limited under the signal normal condition of being considered, the modulus of sampling value is handled can replace by Nyquist (Nyquist) theory and is undertaken, and this is obvious for those skilled in the art.

Disperse if ignore the time, but the received signal pattern turns to

X _i(t)=α _iS (t-Δ)+m _i(t) equation 1

Here α _iBe the signal amplitude of the reception of burst i, because of channel its amplitude that decays changes.m _i(t) be the noise of burst i and disturb and.In-individual cellular system, disturb from the user in the other sub-district of penetrating that takes place frequently.Because noise power E[|m _i(t) | ²] intensity changes usually between burst, so noise right and wrong static state.For example and since interference signal be decay or because the jump of system's medium frequency, just can this thing happens.Yet in a burst, noise is considered to white noise or static noise usually.

Be used to estimate that the technology algorithm state of Δ is called as non-coherent integration (ICI), for example described in the United States Patent (USP) sequence 08/978,960 of on November 26th, 1997 application, as a reference at this.In essence, this algorithm carries out in the following manner.Definition

C _i(Δ)=∫ S (t-Δ) X _i ^*(t) the dt equation 2

This is at the received signal X relevant with burst i _i(t) and the correlated results between the known array S (t).If SNIR is low, C _i(Δ) has peak value at double, and it is used among Fig. 2 | C _i(Δ) | ²Curve representation.Calculate

$g\left(\mathrm{\Δ}\right)=\underset{i=1}{\overset{I}{\mathrm{\Σ}}}{\left|C_i\left(\mathrm{\Δ}\right)\right|}^2$ Equation 3

And select the Δ that makes g (Δ) maximum ^*(being its value).Fig. 3 and 4 represents the example of I=10 and I=50g (Δ) respectively.Be on duty mutually in disturbed condition (non-static noise) ICI execution.

The modification of ICI is the ICI of weighting, carries out in the following manner.Allow

$g_W\left(\mathrm{\Δ}\right)=\underset{i=1}{\overset{I}{\mathrm{\Σ}}}{W}_i{\left|C_i\left(\mathrm{\Δ}\right)\right|}^2$ Equation 4

And select and make g _wThe Δ that (Δ) is maximum ^*W _iBe the weight coefficient of design, for example be burst that amplifies high SNIR and the burst that compresses low SNIR.As by with Fig. 3 and 4 same Fig. 5 (I=10) and 6 (I=50) shown in relatively like that, this is feasible than with equation 3 how visible peak value being arranged.Calculating weight coefficient is very complicated thing.The optimum weighting coefficient relies in the SNIR of relevant burst, but SNIR can not estimate, up to Δ ^*Known (or estimated).Like this, when using equation 4, need Δ ^*Remove to estimate Δ ^*An approach that proposes this problem is to carry out Δ ^*Priori estimation, and determine weight coefficient W with it _iYet a such priori estimation often can make some mark spaces depart from corrected value unfriendly.In addition, before the equation 4, the ICI of weighting also requires to collect and store the signal X of all receptions on calculate _i(t), this equation 4 is a disadvantageous restriction in a lot of the application, and for example, storage capacity generally is restricted in mobile radio receiver.

Though under non-static noise (interference) condition, can accept the execution of weighting ICI, its implementation status clumsiness under static white noise condition.

Wish because above explanation provides the burst of performance improvement under static and the non-static noise condition to detect, and do not require the significant data storage capacity.The present invention is based on the correlation that transmits and receives between signal, also, provide such burst to detect by implementing an accumulation algorithmic function, to estimate the propagation delay of this burst based on the energy of these signals.

The accompanying drawing summary

Fig. 1 illustrative wherein can be implemented an example communication system of the present invention.

The correlation function of a prior art of Fig. 2 illustrative.

Fig. 3 and 4 illustrative prior art non-coherent integration (ICI) results' example.

Fig. 5 and 6 illustrative prior art weighting ICI results' example.

Fig. 7 and 8 illustrative are by example technique of the present invention, are used to estimate the radio propagation time between a radio transmission station and the radio reception station.

Fig. 9 explanation is by the appropriate section of the exemplary embodiment at a radio reception station of the present invention.

One exemplary embodiment of Figure 10 key diagram 9 factor of determinations.

The operation of Figure 11 illustrated example, it can be carried out by the radio reception station of Fig. 9 and Figure 10.

Figure 12 illustrates exemplary prior art propagation time estimating techniques and by the comparison between the exemplary propagation time estimating techniques of the present invention.

Describe in detail

Press embodiments of the invention, from the propagation time that the radio signal at a radio reception station, a radio transmission station to is propagated can be based on the relevance values that calculates, calculated energy value and a known energy value are estimated.As mentioned above, receiving station receives a series of received signals that correspond respectively to by the radio signaling burst of this radio transmission station emission.Each radio signaling burst comprises a known signaling sequence.The correlation indication received signal of aforementioned calculation and the correlation between known array, the energy value of aforementioned calculation calculates each received signal, and the energy that above-mentioned known energy value is this known array.

By exemplary embodiment of the present invention, can estimate the propagation time Δ with following formula:

Equation 5

$g_{\log }\left(\mathrm{\Δ}\right)=\underset{i=1}{\overset{I}{\mathrm{\Σ}}}{f}_i\left(\mathrm{\Δ}\right)=\underset{i=1}{\overset{I}{\mathrm{\Σ}}}\log (E_S{E}_{\mathrm{xi}}-{\left|C_i\left(\mathrm{\Δ}\right)\right|}^2)$

Here E _SBe the energy of known transmitting sequence S (t),

E，＝∫|s(t)| ²dt，

And E _XiBe received signal X _i(t) energy,

ε _xi＝∫|x _i(t)| ²dt

g _Log(Δ) function is flat-footed relatively, thereby calculates simple relatively.For example, this logarithm can use look-up table well known in the prior art to finish.In addition, when receiving each signal X _i, the signal X that can calculate corresponding logarithm and be added to simply and received in the past _iRelevant logarithm existing and.Like this, can implement g _LogMeasure and do not store any signal X that formerly receives _iThereby the needs that data are stored are reduced to a minimum.When implementing this g by a mobile receiving station _LogDuring measurement, this point is a particular importance, because be restricted in the ability of the sort of occasion data storing.

The g of Fig. 7 and 8 usefulness curve shows equatioies 5 _LogMeasure.In Fig. 7 example, use 10 bursts (I=10), and in Fig. 8 example, use 50 bursts (I=50).As shown in FIG. 8, produce minimum g _LogThis value Δ of value is selected as transmitting and receiving the propagation time between the station.In Fig. 8, make g _LogFor the value Δ of minimum is designated as Δ ^*

In appendix, point out, make g _LogMinimum value Δ ^*Maximum likelihood estimation Δ under some (very general) condition.

Fig. 9 explanation is by an exemplary embodiment relative section at a radio reception station of the present invention (as shown in FIG. 1).In the receiving station of Fig. 9, the radio signal that common radio receiving equipment 91 receives from the cell site by a radio communication channel 93.This receiver device 91 can use ordinary skill to produce the received signal X of corresponding emission burst i from this cell site _iThis received signal X _iBe input to factor of determination 95, it implements equation 5 is used for any desired position application with generation Δ ^*

Figure 10 exemplary embodiment of the factor of determination 95 of figure key diagram 9.Received signal X _iBe input to energy calculator 101, it uses ordinary skill to calculate E _XiSignal X _iAlso be input to correlation calculator 102, it also receives in fact known training sequence S (t) as input.Select the value of Δs for all, correlation calculator 102 can use ordinary skill the amplitude of the correlation function of 104 output equatioies 2 square.Received signal X _iENERGY E _XiBe multiplied by the known energy E of known signal S (t) by multiplier 105 _SFor all g _LogCalculate E _STo be same predetermined constant, and can provide easily or calculating in advance.At subtraction device 107, the output of correlation calculator 102 104 with from the long-pending Es of multiplier 105 in 108 outputs _SE _XiCombined.The output E of subtraction device 107 _SE _Xi-| C _i(Δ) | ²Be added to logarithm lookup table 109 any suitable device of logarithm (or be used for determining), it produces the function f by the requirement of equation 5 _i(Δ).Then this function is applied to summation accumulator 100 to produce desired function g _Log(Δ).Point out according to equation 5, for example, at 10 bursts (i=10) afterwards,

Like this, for each additional received signal X _i, calculate g easily by summation accumulator 100 _Log, do not need to store any signal X that formerly receives _i, and as long as by will be for present signal X _iF _i(Δ) is added to the signal X that receives corresponding to formerly _iF _iValue add up and.A minimum detector 106 receives g from summation accumulator 100 _Log(Δ), detection function g _LogThe minimum value of (Δ), and output is corresponding to the minimum value Δ of this detection ^*(referring to, for example, Fig. 8).

The operation of Figure 11 illustrated example, it can be carried out by the factor of determination of Fig. 9 and 10.110, receive present signal x _i111, calculating energy E _Xi112, ENERGY E _XiMultiply by known energy E _S113, calculate | C _i(Δ) | ², 115, determine | C _i(Δ) | ²And energy product E _SE _XiBetween poor.116, determine this poor (be f _i(Δ)) logarithm.117, this logarithm is added to adding up of logarithm and (corresponding to received signal X formerly _i) to produce g _Log(Δ).

Determine whether to handle enough signal X 118 _iTo form definite Δ ^*Trial.If then attempt to try to achieve g 119 _LogThe minimum value of (Δ) and corresponding Δ ^*For example, if processed signal X _iThe predetermined nominal number of threshold values, then can carry out this trial 119.Determine whether to handle enough signal X 120 _iTo be provided at 119 Δs of determining ^*Confidence level.If, at 121 output Δs ^*For example, as long as consider g _LogThe minimum value sufficiently clear that the is determined ground of (Δ) is from g _LogThe consecutive value of (Δ) is differentiated out, then can export Δ 121 ^*, (for example, to be different from consecutive value) more than a predetermined threshold amount.118 or 120, if determine also not have enough signal X _iBe carried out processing, then next signal X _iWait for 110.In such a way, in case reached and handled enough signal X _iJust can determine Δ ^*In an example,, 10 signal X can handled 119 _iAttempt afterwards, but, only handling 50 signal X 121 _iCould export Δ afterwards ^*

Figure 12 uses an exemplary comparison in equation 3,4 and 5 estimation propagation times with curve shows.On trunnion axis, represent carrier wave SNIR with dB, and TOA standard of appraisal deviation (std) (that is Δ, ^*Standard deviation) be that unit representation is on vertical axis with the mark space.The simulation of carrier wave and interference signal is a binary phase shift keying (BPSK) modulation sequence in this embodiment, is independently propagating on smooth Rayleigh (Rayleigh) the decay channel.The burst number that uses is I=50.Respectively with 121,122 and 123 expression equatioies 3,4 and 5 results.The technology of the present invention of equation 5 obviously is dominant in this embodiment, especially in low SNIR grade.

It will be apparent to one skilled in the art that invention described above implements easily, for example arrive and pass through software, hardware or both suitable improvement in the measurements/processing section in the common time of common radio receiving station.

Though below described exemplary embodiment of the present invention in detail, this does not limit the scope of the invention, it can be put into practice in various embodiments.

Claims (22)

1. A method of determining the travel time of a propagated radio signal from a radio transmitting station to a radio receiving station, said comprising: The receiving station receives a series of received signals respectively corresponding to radio signaling bursts transmitted periodically successively in time by a radio transmitting station, said series of received signals being offset from each other by a predetermined amount of time, each said The radio signaling burst consists of a common signaling sequence known at the receiving station; computing a plurality of correlation values for each received signal, the correlation values representing the correlation between the received signal and the known sequence, the correlation values being used as possible values for the plurality of propagation times; Calculate the energy value of each received signal; and The propagation time is estimated based on the calculated correlation value, the calculated energy value and a known energy value associated with the known sequence. 2. The method of claim 1, including the step of using said estimated travel time to determine the geographic location of one of the transmitting station and the receiving station. 3. The method of claim 1, wherein said step of estimating comprises: for each received signal, multiplying the calculated energy with the known sequence energy to produce an energy product; and for each received signal, correlating the energy product with the corresponding Values are combined to produce a combined value. 4. The method of claim 3, wherein for each received signal, said step of estimating includes determining the logarithm of the corresponding combined value to produce a logarithm value. 5. The method of claim 4, wherein for each of the plurality of possible values of the time of flight, said step of estimating comprises summing the logarithmic values of the corresponding received signals to produce a plurality of summed values respectively corresponding to the plurality of possible values of the time of flight . 6. The method of claim 5, wherein said estimating step includes identifying the smallest one of said summed values and identifying the corresponding travel time value as the estimated travel time. 7. The method of claim 3, wherein said combining step includes determining the difference between energy products and corresponding correlation values to produce a combined value. 8. The method of claim 7, wherein, for each received signal, said step of estimating includes determining the logarithm of the corresponding combined value to produce a logarithm value. 9. The method of claim 8, wherein, for each of the plurality of possible values of the time of flight, said step of estimating comprises summing the logarithmic values of the corresponding received signals to produce a plurality of summed values respectively corresponding to the plurality of possible values of the time of flight . 10. The method of claim 9, wherein said estimating step includes identifying the smallest one of said summed values and identifying the corresponding travel time value as the estimated travel time. 11. The method of claim 3, wherein, for each received signal, said step of calculating a correlation value comprises calculating a correlation value between the received signal and a known sequence for possible values of a plurality of propagation times, and squaring The magnitude of the calculated correlation value to generate the correlation value. 12. The method of claim 11, wherein for each received signal, said step of estimating includes determining the logarithm of the corresponding combined value to produce a logarithm value. 13. The method of claim 12, wherein for each of the plurality of possible values of the time of flight, said step of estimating comprises summing the corresponding logarithmic values of the received signal to produce a plurality of sums respectively corresponding to the possible values of the time of flight value. 14. The method of claim 13, wherein said estimating step includes identifying the smallest one of said summed values and identifying the corresponding travel time value as the estimated travel time. 15. An apparatus for determining the propagation time of a radio signal transmitted from a radio transmitting station to a radio receiving station, comprising: a radio receiver for receiving a series of received signals respectively corresponding to radio signaling bursts periodically successively transmitted in time by a radio transmitting station, the series of received signals being offset in time from each other by a predetermined amount of time, each of said radio signaling bursts includes a common signaling sequence; a determinant connected to said radio receiver for receiving said received signal therefrom, said determinant having an input for receiving information representing said common sequence, said determinant comprising: a correlation calculator for calculating a plurality of correlation values for each of said received signals in response to said received information and said received signals used for calculation, the plurality of correlation values representing the correlation between the received signal and said common sequence a correlation, where multiple correlation values are used as possible values for multiple travel times; an energy calculator, which calculates an energy value for each received signal; and The determinant estimates the propagation time based on the calculated correlation value, the calculated energy value and a known energy value associated with the common sequence. 16. The apparatus of claim 15, comprising an output connected to said decision factor for outputting a mobile location application information representative of the estimated travel time. 17. The apparatus of claim 15, wherein the apparatus is provided in a mobile radio receiving station. 18. The apparatus of claim 15, wherein said decision factor comprises a multiplier connected to said energy calculator for multiplying the calculated energy value of each received signal by said known energy value to produce an energy said determinant also includes a combining device connected to said multiplier for combining the energy product of each received signal with its corresponding correlation value to produce a combined value. 19. The apparatus of claim 18, wherein said determinants further comprise a logarithmic determinant coupled to said combining means for determining respective logarithmic values responsive to the combined value associated with each received signal. 20. The apparatus of claim 19, wherein said determinant further comprises a summation accumulator connected to said logarithmic determinant, and the summation accumulator obtains a resultant value for each of a plurality of possible values of propagation times The corresponding logarithmic values of the received signals are summed to produce a plurality of summation values respectively corresponding to the plurality of possible values of the propagation time. 21. The apparatus of claim 20, wherein said determinant comprises a detector connected to said summation accumulator for identifying the smallest one of said summation values and identifying the corresponding travel time as the estimated travel time . 22. The apparatus of claim 15, wherein the apparatus is provided in a fixed location radio receiving station.

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